The present inventors have already found five species of glycoglycerophospholipids (phosphocholine-containing glycoglycerolipids) from MT-4 cells (human helper T cells infected with HTLV-I (human lymphotropic retrovirus Type I), Miyoshi et al., Gann., 71, 155-156 (1980)). The present inventors have been previously found that one of the five species of glycoglycerophospholipids is 6'-O-phosphocholine-.alpha.-glucopyranosyl-(1'-3)-1,2-diacyl-sn-glycerol (Shishitsu-Seikagaku-Kenkyu (Studies on Lipid Biochemistry), Vol. 35, pp. 111-114, 1993).
On the other hand, it has been reported that Mycoplasma fermentans is an exacerbation factor of human acquired immunodeficiency syndrome (AIDS) (Lo. S., -C. et al., 1991, Science, 251: 1074-1076; U.S. Pat. No. 5,242,820), or Mycoplasma fermentans is a cause of rheumatism (Williams, M. H. et al., 1970, Lancet ii: 277-280).
Various antibodies against mycoplasmas have been hitherto known, and they have been also used for clinical examination. However, the majority of them are antibodies against Mycoplasma pneumoniae or Mycoplasma genitalium. Monoclonal antibodies against these mycoplasmas have been also prepared. However, it is presumed that such an antibody is an antibody which recognizes a protein of a mycoplasma, or simultaneously recognizes a protein and a lipid of a mycoplasma.
Further, any of such antibodies does not exhibit specificity to Mycoplasma fermentans (Japanese Patent Laid-open Nos. 63-298, 63-184064, 63-32496, end 5-304990, and U.S. Pat. Nos. 5,158,1370, 4,945,041, and 5,242,820). An antibody, which exhibits specificity to Mycoplasma fermentans, is disclosed in U.S. Pat. No. 5,242,820. However, this antibody is obtained by using an entire extract of mycoplasmal cells as an immunogen, and thus the antibody is regarded as an antibody which recognizes a protein. Accordingly, if a mycoplasma contained in a body fluid such as a serum which contains various proteins is detected by using this antibody, the antibody highly possibly makes nonspecific binding. Therefore, it may be impossible to expect a high sensitivity. Further, when an antigen is a protein, it is sufficiently assumed that antigenicity disappears due to mutation in an amino acid sequence of the protein.
As far as the present inventors know, it has not been reported that any mycoplasma has a glycoglycerophospholipid containing phosphocholine. further, no instance has been known, in which a glycoglycerophospholipid originating from a mycoplasma is used as an immunogen to obtain an antibody which exhibits specificity to the glycoglycerophospholipid. Moreover, it has not been known at all as well that the antibody, which exhibits the specificity to the glycoglycerophospholipid, exhibits high specificity to Mycoplasma fermentans.